1. Field of the Invention
The present invention relates to a frequency sensitive type shock absorber, and more particularly, to a frequency sensitive type shock absorber which is capable of minimizing a rise in costs and is advantageous to the design of basic components in implementing performance showing different characteristics according to frequency areas so as to maximize a ride comfort.
2. Description of the Related Art
In general, suspension systems are installed in vehicles so as to improve a ride comfort by absorbing and damping a vibration or shock which is transferred from a road surface to an axle during driving. As one of such suspension systems, a shock absorber is used.
The shock absorber is installed between an axle and a vehicle body, and includes a cylinder in which a piston rod is movably installed.
In addition, the cylinder is filled with gas or oil. A damping force is generated while the oil is moved by a piston valve installed in an end portion of the piston rod.
However, such a general shock absorber has a limitation in that it has a constant damping force characteristic with respect to a condition of a road surface or a posture change of a vehicle. Therefore, in the case of decreasing the damping force characteristic, the ride comfort can be improved, but the posture of the vehicle cannot be stably maintained.
On the contrary, in the case of increasing the damping force characteristic, the posture of the vehicle can be stably maintained, but the ride comfort is deteriorated. Therefore, there is a problem that the damping force characteristic of the shock absorber cannot be adjusted according to the condition of the road surface or the posture of the vehicle.
A frequency sensitive type shock absorber has been developed which can more finely adjust a damping force characteristic according to a condition of a road surface or a posture change of a vehicle so as to improve a ride comfort. Such a conventional frequency sensitive type shock absorber is disclosed in Korean Patent Publication No. 10-2013-0025818.
However, such a conventional frequency sensitive type shock absorber limits its driving by using a slidable free piston and a caulking spring to absorb a fluid and open/close a passage.
Therefore, a long stroke is required for absorbing a necessary amount of a fluid. Due to a large momentum, a noise is generated by a contact of a free piston, and a durability of a part is degraded.
Furthermore, a structure for opening/closing a passage is complicated for implementing performance. Since a large number of parts are used, costs are increased and it is disadvantageous to mass production and automation.